Aluminum fluoride-based catalyst for the gas-phase fluorination of hydrocarbons

ABSTRACT

A CATALYST IS DISCLOSED FOR PREPARING FLUORINATED OR CHLOROFLUORINATED HYDROCARBONS BY FLUORINATION OR CHLOREFLUORINATION OR DISPROPORTIONATION REACTIONS OR CHLOPHASE, WHICH CATALYST COMPRISES ALUMINUM FLUORIDE CONTAINING MINOR QUANTITIES OF ZINC, CHROMIUM, NICKEL AND PREFEABLY ALSO IRON COMPOUNDS WHICH ARE PRESENT IN QUANTITIES CORRESPONDING TO THE FOLLOWING PRECENTAGES BY WEIGHT OF METAL BASED ON THE TOTAL: FROM 0.05 TO 5% ZN, FROM 0.05 TO 5% CR, FROM 0.05 TO 5% NI, AND UP TO 3% FE. THE ZINCE, CHROMIUM, NICKEL AND IRON, IF ANY, ARE PRESENT AT LEAST PARTLY IN THE FORM OF HALIDES, IN PARTICULAR FLUORIDES, OR OXIDES OR OXY-HALIDES. A PROCESS FOR PARPARING THE CATALYST IS DISCLOSED, AS WELL AS VARIOUS DETAILS RELATING TO THE AFORESAID PROCESS FOR USING THE CATALYST.

United States Patent US. Cl. 252-442 2 Claims ABSTRACT OF THE DISCLOSUREA catalyst is disclosed for preparing fluorinated or chlorofluorinatedhydrocarbons by fiuorination or chlorofluorination or disproportionationreactions in the gas phase, which catalyst comprises aluminum fluoridecontaining minor quantities of zinc, chromium, nickel and preferablyalso iron compounds which are present in quantities corresponding to thefollowing percentages by weight of metal based on the total: from 0.05to 5% Zn, from 0.05 to 5% Cr, from 0.05 to 5% Ni, and up to 3% Fe. Thezinc, chromium, nickel and iron, if any, are present at least partly inthe form of halides, in particular fluorides, or oxides or oxy-halides.A process for preparing the catalyst is disclosed, as well as variousdetails relating to the aforesaid processes for using the catalyst.

This invention relates to new catalysts for the gas-phase fiuorinationof halogenated hydrocarbons and for the chlorofiuorination of ethylene.These catalysts are characterized in that they make it possible to formgreater quantities of symmetrical compounds or compounds having arelatively higher degree of symmetry as compared with those obtainedwhen using known catalysts. The expression degree of symmetry as usedherein refers to the distribution of the fluorine atoms and it is alsointended that a not entirely symmetrical compound such as has a higherdegree of symmetry than the CF -CCl isomer.

It is well known that many metal compounds show a catalytic effect inthe gas-phase fiuorination of halogenated hydrocarbons with HF: inparticular, British Pat. No. 428,361 e.g. cities the Fe, Ni, Co, Mn, Cd,Zn, Hg and many other halides, as well as some combinations thereof.French Pat. No. 1,380,938 mentions as known the catalytic activity ofthe Al, Fe, Cr, Mn, Ni, Zn and many other metal halides, in theaforesaid reaction.

The particular catalytic composition according to the present invention,however, does not appear to be known, and distinguishes itself i.e. bythe above said selective catalytic eifect.

The catalyst according to this invention consists essentially ofaluminum fluoride containing minor quantities of zinc, chromium, nickeland preferably also iron compounds, which have been uniformlydistributed on the aluminum fluoride granules, e.g. by treating thealuminum fluoride itself with solutions of salts of the aforesaidmetals.

The quantities of zinc, chromium and nickel and iron compounds to beadded to the aluminum fluoride-based 3,793,229 Patented Feb. 19, 1974ice catalytic composition must be such as to be within the followinglimits, based on the weight of metal in the total:

from 0.05 to 5% zinc from 0.05 to 5% chromium from 0.05 to 5% nickel upto 3% iron.

Instead of aluminum fluoride, it is also possible to employ alumina inthe catalyst preparation. Said alumina is then substantially convertedinto fluoride in a later fiuorination treatment of the catalyticcomposition with gaseous HF. When using alumina for preparing thecatalyst, it will be necessary to use greater quantities of zinc,chromium and nickel compounds, i.e. quantities corresponding to thehigher percentages indicated herein above.

Zinc, chromium, nickel and iron are added to the aluminum fluoride-basedcatalytic composition preferably in the form of solutions of theirsalts, such as e.g. their nitrates and chlorides, which are caused to beabsorbed by the starting aluminum fluoride or alumina. The thus-obtainedcomposition is dried in an oven at about C.

In the preparation of the catalyst, there are employed preferably zinc,chromium, nickel and, optionally, iron compounds in the form of halidesor other compounds, in particular nitrates, which, after the activationand fiuorination treatment of the catalytic composition, will be presentat least partly in the form of halides, particularly fluorides, oroxides or oxy-halides.

The aluminum fluorideor alumina-based composition together with theaforesaid added metal compounds is then subjected to an activationtreatment, which is effected by heating the product in a flow of air ornitrogen for a period of 0.5 to 4 hours at a temperature ranging from300 to 550 C.

For the catalyst prepared by starting from alumina, a subsequentfiuorination is necessary. This is performed by heating the activatedproduct in a flow of gaseous HF suitably diluted with air or nitrogen oranother inert gas, at a temperature ranging from 200 to 500 C.

HF is diluted principally for the purpose of controlling more easily thereaction temperature and avoiding local overheating.

The treatment with HF may be advisable also for the catalyst that isobtained by starting from aluminum fluoride. The catalyst may beprepared in fine granules adapted to be used in fluidized bed reactors.

The preparation of the catalyst according to the present invention isillustrated in detail below in Examples 1 and 4 (starting from aluminumfluoride) and in Example 1 bis (starting from alumina).

The catalyst according to this invention is particularly useful in thefollowing reactions:

(a) Gas-phase fiuorination with HF of halogenated ethanes containing atleast one chlorine atom, at a temperature ranging from 250 to 500 C. inorder to obtain fluorinated or chlorofluorinated ethanes with highyields of compounds having a high degree of symmetry with respect to thefluorine atoms; in particular, fiuorination of CF ClCFCl obtaining highyields of the symmetrical product CF ClCF Cl and reduced isomerizationof the starting product into CF CCI (b) Gas-phase chlorofluorination ofhydrocarbons having two carbon atoms optionally partly halogenated, witha Cl +HF mixture, in the presence of recycled halogenated hydrocarbons,at a temperature between 250 3 and 500 C., in order to obtainprevailingly C F Cl C F Cl and C F Cl with high percentages of isomershaving a high degree of symmetry, i.e. CF ClCF Cl, CF ClCF C1 and CFClCFCl (c) Disproportionation reaction of CF ClCFCl in the gas phase, at atemperature ranging from 250 to 500 C., with formation of thesymmetrical compound CF ClCF Cl.

It should be kept in mind that above the indicated limit of 500 C., theselectivity of the catalyst in promoting the formation of symmetricalproducts decreases with increase in temperature.

The use of the catalyst according to the present invention in theaforesaid reactions is illustrated in Examples 2, 3, 4, 5, 6 and 7reported hereinafter which, on the other hand, are not intended in anyway to limit the invention as regards the use of said catalyst.

EXAMPLE 1 Preparation of the catlyst starting from aluminum fluoride Thecatalyst was prepared by pouring the solution of active elements ontoaluminum fluoride (obtained by fluorination of alumina) havlng thefollowing chemical and physical characteristics:

It has a fluorine content of 64.2% It contains the following elementsdetermined by emission spectrograph:

Percent Be 0.0014 Ca 0.032 Cr 0.005 Cu 0.00019 Ga 0.0087 Fe 0.018 Mg0.0096 Mn 0.0005

Mo 0.0048 Ni 0. 005 Si 0.060 Na 0.021 Pb 0.001

On the basis of X-ray examination, it appears to consist of gamma-MPwith the presence of beta-AlF pursuant to the definitions given inFrench Pat. No. 1,383,927.

It has the following particle size distribution, as determined usingsieves of the Tyler series.

Mesh: Percent 120 5.2 140 149 170 13 4 200 162 230 18 8 270 12 8 32512.8 More than 325 5.8

The solution of active elements is poured onto 630 grs. of this aluminumfluoride, while being stirred slowly and continuously. Said solution ofactive elements is prepared by dissolving 26.4 grs. NiCl .6H O; 25.2grs. CrO 3.16 grs. FeC1 .6H O; and 6.82 grs. ZnCl in water heated to 80C., so that the final solution has a volume of 107 cm. corresponding tothe total volume of the pores of the aluminum fluoride to beimpregnated.

The thus-impregnated aluminum fluoride is allowed to rest for 4 hoursand is then dried at 150 C. for 12 hours in a fluidized bed with airflow. The activation with air and subsequently the fluorination withhydrofluoric acid are conducted in an Inconel reactor having a cm.diameter, at a linear gas velocity of about 9 cm./sec., as follows:

Activation: The whole is heated to 300C. in an air flow, and thistemperature is maintained for one hour; the whole is then cooled from300 C. in 200 C. in. 30 min., still in an air flow.

Fluorination: The whole is heated in a flow of air and hydrofluoric acid(10:1 by volume) up to 400 C. in minutes, and is maintained at thistemperature for one hour, whereafter it is cooled.

EXAMPLE 1 BIS Preparation of the catalyst starting from alumina Aluminais employed which has the following chemical and physicalcharacteristics:

Form: Spheroidal Superficial area m. /gr 280 Volume of pores cc./gr 0.45Apparent specific weight grs./cc 0.92

Average composition:

A1 0 97.46 Na O 0.06 510 1.80 S0 0.66 Fe 0.015

Loss on calcination: 20% at 450 C. for 4 hours. The particle sizedistribution of the starting alumina, determined using sieves of theTyler series, was as follows:

Mesh: Percent 7.3 16.3 170 13.1 200 14.5 230 14.5 270 11.3 300 11.3 3008.8 More than 300 14.3

58 grs. ZnCl 32.6 grs. NiCl .6H O; and 121 grs. CrCl .6H O and a littlewater are mixed while hot. The thus-obtained solution is diluted up to avolume of 370 cc., which corresponds to the total volume of pores of thealumina which is to be impregnated.

This solution is poured slowly onto 1,000 grs. alumina kept under slowand continuous stirring both during the impregnation and for the twofollowing hours. The whole is then allowed to rest for 4 hours and driedat C. in an oven for 12 hours. The impregnated alumina is poured into anInconel reactor having a 5 cm. diameter wherein, the linear gas velocitybeing about 9 cm./sec., the steps of activation with air and then thefluorination with hydrofluoric acid are carried out in the followingmanner:

Activation: The whole is heated in a flow of air from 25 to 500 C. in 4hours. Temperature is kept at 500 C. for 30 minutes and then caused todiminish (still in a. flow of air) from 500 to 200 C. in two hours.

Fluorination: The composition is heated in an air flow to 250 C., then,at 250 C., a mixture of air and HF is fed for 9 hours. The totalquantity of HP is 1,450 grs.

Temperature is then caused to rise from 250 to 420 C. in a flow of aironly. An additional fluorination is effected at 420 C. using a mixtureof air and HF for 4.30 hours. The quantity of HF fed is 600 grs.Finally, the system is cooled from 420 to 200 C. in a flow of air.

EXAMPLE 2 Gas phase fluorination of CF ClCFCl The fluorination reactionwas carried out in a nickel reactor containing the aluminumfluoride-based catalyst with variable quantities of chromium, nickel,zinc and iron, and with an equimolar ratio of the reactants HF and CFClCFCl The reaction products were neutralized with caustic soda, andthen condensed. The composition of the mixture was determined bygas-chromatographic analysis and, for the isomers, by LR. absorptionspectra. Table 1 contains the results after 5 hours operation, of theruns eflected both using the catalyst according to the present inventionand catalysts having a different composition, for the purpose ofcomparison.

EXAMPLE 3 Chlorofluorination of ethylene Ethylene chlorofluorinationruns were carried out in the gas phase in the presence of both catalystsaccording to this invention, and diflerent catalysts, for the purpose ofcomparison. The results of these runs are shown in Table 2.

The runs were conducted in a nickel reactor containing the aluminumfluoride-based catalyst, with variable quantities of zinc, iron, nickeland chromium, by feeding the reactants C H C1 and HF together withrecycle products (chlorofluorinated hydrocarbons) whose composition isindicated in Table 3.

The reaction product was subjected to distillation. The tail fractionwas recycled into the reactor. The head fraction principally consistedof a mixture of C F Cl, C F Cl C F Cl and C F Cl and furthermore of HFand C1 and HCl. The net yields and the ratios between the variousisomers are indicated in Table 2.

EXAMPLE 4 135 cc. of a solution containing 11.5 grs. ZnCl 20 grs. CrCl-6I-I 0 and 16.3 grs. NiCl -6H O are poured slowly into 800 grs.aluminum fluoride of the same type as in Example 1. The aluminumfluoride is kept under continu- 6 operating conditions mentioned inTable 5. The reaction products are conveyed directly into achromatograph in order to determine their composition.

EXAMPLE 6 A vessel heated to 180 C. is fed continuously with ethylene,anhydrous HF, and a mixture of recycled halogenated hydrocarbons.

These products are then pre-heated to 220 C., then mixed with chlorine,and then fed into a fluidized bed reactor kept at 360 C. by electricheating.

The products coming out of the reactor are conveyed into a stripperwhere the high boiling products are condensed, discharged continuouslyand conveyed into the evaporator by a recycle metering pump. The lowboiling products, which represent the actual reaction product, areneutralized and then conveyed into a collecting device.

The recycled products fed at the beginning of the run consist of amixture of C Cl and C FCI The composition of this recycled stream variesas time goes on until it reaches a composition which is characteristicof the stationary state.

This conversion causes a higher consumption of HF to bring about thefluorine content corresponding to the stationary state. The resultsobtained are shown in Table 6.

EXAMPLE 7 The operations are carried out as in the foregoing Example 6,with the variants described in Table 7.

ous and slow stirring both during the impregnation and TABLE I for thefollowing 3 hours. The system 1s then dried in a Run number 1 2 3 4 5 67 fluidized bed in a flow of air for 12 hours at 150 C. and Aluminumfluoride natal st activated for 2 hours at 350 C. still in a flow ofair. containing; y

560 cc. of this catalyst are fed into an Inconel reactor Ni, Percent 8 3f f f g 8-2 having a 5 cm. diameter and a chlorofluorination run of Zn,percent 0 0 0 1 (15 Z v percent 0. 1 0.8 ethylene 1s eflected at 300 C.according to the procedures Reaction Pump" 0 400 400 400 400 400 330 450indicated 1n Example 3. Table 4 shows the reaction congy t 3 g 25 3 3 3l1 I1 ditrons, the main products obtained and the composition f g fl ggg94 73 154 i3}; 11 g e yte S, 138113811 1 of the recycled mass 3% 5% 0. 1g 1 (2) (2) 0.5 .5 1.9 0.9 EXAMPLE 5 CF 001 1g 40 223 8 7 92. 7 91. 0Disproportioning and isomerization of CF Cl-CFC1 3 a 2 O O O 0 1 Thebalance to 1 consists redominatel of C F 01 tur of Gaseous CF ClCFCl 1scaused to pass through a isomers). 00% p y 2 2 (mm e glass reactorcontaining the catalyst, according to the 2 Traces- TABLE 2 Run number 12 3 4 5 Aluminum fluoride catalyst containing:

N1, percent.... 0 2 0 2 2 Or, percent" 0 0 0 1 1 Fe, percent. 0 0 0 0.09 0. 14 Zn, percent" 0 0 1 0. 92 0. Reaction temp., C 400 400 400 360340 Contact time, sec 1. 7 1. 5 3 3 3 C1z/HF/CzH4 6.1/4. 6/1 5/4 4/1 5.2 5. 4/1 5.56/5. 3/1 5.38/3. 66/1 RecyclelczHi 10/1 10/ 10/1 10/1 10/1HF conversion, percent.-- 86. 3 88.0 72. 4 62. 2 82. l Ethylene conv.,percent--- 1 100 100 100 Net yields 1 incmol 2. 4 1.8 1. s 02111012.-..80.0 74. 1 76.5 11. 4 1. 4 m0 16. 4 23. 0 21. a 88.5 91. 2 021 201 7.3Selectivity:

CFzCl-CFzCl 11 24 46 78 so C2F4C13 CFzCl-CFCI: 54 45 81 99.4 99.4

czFa la CFClz-CFCI: ------100 46.0

C2F3C14 1 M01 ercent with respect to 0111 TABLE 4 Reaction temperature,C 300 Contact time, sec. 3 Cl /HF/C H (in mols) 5.3/7.3/1 Recycle/C H(in mols) 10/ 1 HF conv., percent 39.2 Ethylene conv., percent 100 Netyields (mol percent with respect to C H C F Cl 2 C F Cl 79.9 C F Cl 6.8

Selectivity: Percent CF2C1CF2C1/C2F4Clz 92 CF ClCFCl /C 'F Cl 99.9(:F(:2F2cl4 93 Composition of recycle: (Percent by weight) C F Cl 5-0 CCl F 0.5 C F Cl 67.2 C Cl 12.6 C FCl 13.8 C Cl 0.9

TABLE 5 Run number 1 2 3 4 5 6 7 Aluminum fluoride catalyst containing:

Ni, percent 2 0 0 2 2 2 Cr, percen 0 0 2 0 1 1 1 Zn, percent... 0 0 0 11 0.8 0.6 Reaction temp. 400 400 400 400 400 400 320 Contact time, s 3 33 3 3 3 3 CFzClCFC1z conv., percent. 99 97 99 42 27 45 18 Net yield in-CZFECI 4.6 14.8 12.7 7.6 12.2 9.1 0412012 23.7 13.9 17 35.7 27 32 54.5CFSCC13 38.9 27.9 28 0.1 0.1 0.1 CzFgCh 32.8 43.9 42,3 50 50 50 45.5

In runs 4 and 6, CzF4Clz consists predominately of the CFzCl-CFzOl'isomer; in 11111 7 it represents 91% while in run 1 it represents 17%.

TABLE 6 Catalyst composition: Ni=0.5/Cr =0.5/Zn=1% Recyc1e/Cl /HF/C /C H=/5.95/4.74/1 (in mols) Reaction temperature=360 C.

Contact time sec7=3 Linear velocity=5 cm./ sec.

Duration of run=3 h.

Reactants fed (in mols) Organic products obtained (in mols) Recycle atend of run:

CF ClCFCl 0.043 CF -CCI 0.001 C HCl 0.018 C F Cl 0.350 C Cl 0.307 C FCI0.236 0 01 0.198 HF conversion, percent 75.7 C1 conversion, percent 85.5C H conversion, percent Reaction products:

C F Cl 0.004 CF Cl-CFCl 0.497 CF -CCI 0.003 CFC1=CC1 0.011 C HCl 0.016C2F2C14 0.400 C Cl 0.064 C FCl 0.011 CF ClCFCl /C F Cl percent 99.3

TABLE 7 Catalyst composition: Ni=2% Cr=1% Zn=1.3%

Recycle/ Cl /HF/ C H =10/ 5.5 6.44/ 1 Reaction temperature=360 C.

Contact time sec.-=3

Linear velocity=5 cm./sec.

Duration of run=2 h.

Reactants fed (in mols):

C H 0.653 C1 3.600 HF 4.200

Initial recycle:

C FCl 0.320 C 01 0.990

Organic products obtained (in mols) Recycle at end of run:

CF ClCFCl 0.015 CF CCl 0.0001 C FCl 0.008 C HCI 0.029 CFCl CFCI 0.348CF2C1-CC13 0.047 C Cl 0.467 C FC1 0.214 (3 01 0.222 HF conversion,percent 43.5 C1 conversion, percent 82.0 C H conversion, percent 100Reaction products:

CF Cl-CFCI 0.141 CF -CCI 0.001 C H Cl 0.011 C HCI 0.026 CFClg-CFCI 0.238CF3C1-CC13 0.032 C 01 0.067 C FCl 0.014 C 'CI 0.003 CF Cl-CFCl /C F Clpercent 99.7 CF Cl CFCl C F Cl percent 88 What is claimed is:

1. A catalyst useful for the preparation of fluorinated orchlorofluorinated hydrocarbons by iiuorination, chlorofluorination, ordisproportion reactions in the gas phase consisting essentially ofaluminum fluoride containing 9 10 minor quantities of zinc, chromium andnickel, essentialfluorinating the catalyst by heating to 200 to 500 C.ly in the form of halides, oxides or oxy-halides, wherein in an HP flowdiluted with inert gas to thermally the quantities of zinc, chromium,and nickel correspond control the reaction. to the following percentagesby weight of metal based on the total: from 0.05 to 5% Zn, from 0.05 to5% Cr, 5 References Cited andfrom (105m 5% UNITED STATES PATENTS 2. Aprocess for prepanng the catalyst of claim 1 com 3 650 987 3/1972Vecchio et al 252442 prising adding zinc, chromium and nickel compoundsin the g g "i""' 52 form of halides or compounds which after activation10 ecc l e a 3,476,817 11/1969 Vecch1o 252-442 X and fluorinationtreatments are present essentially in 3 395 187 7/1968 Ch t h 252 442 Xthe form of halides, oxy-halides or oxides to an alu- 3432562 3/1969 G 10P 252:442 X mlnum compound selected from the group consistar HerPATRICK P. GARVIN, Primary Examiner aluminum fluoride and alumma 15activating the catalyst by heating same to a tempera- CL ture between300 and 550 C. in a flow of nitrogen 260 653.7 or air from 0.5 to 4hours and

